It is known to manufacture cadmium electrodes using, as a starting material, only cadmium hydroxide (the discharged state of the cadmium electrode) which is obtained by a complex and costly procedure involving electroplating a cadmium nitrate complex on a porous screen followed by a charging process which converts this complex to cadmium. The cadmium forms a porous compressible body which is then pressed into the screen to the desired final thickness. The cadmium is then completely discharged to become cadmium hydroxide. In such a process, however, it is usually desirable to reduce by a partial charging operation some of the cadmium hydroxide to metallic cadmium before introduction of the electrode into a cell, to provide excess discharge capacity in the negative electrode to counter what is commonly called "fading". While the phenomenon of fading is not completely understood, apparently, during the life of the cell, some of the active material of the negative electrode no longer is easily reduced or oxidized. By providing an excess charge capacity in a negative electrode with respect to the positive electrode, such lost capacity can be compensated for.
To avoid the necessity of using any such costly, cumbersome, electroplating and charge-discharge operations, it has been proposed to mix cadmium oxide and cadmium powders together in the desired proportions and then add a binder-forming paste thereto which is applied to a screen. The coated screen is then placed in an oven to provide a dry coating of the active material mix. (One such process is disclosed in U.S. Pat. No. 3,888,655.) In one electrode made by this process, it was noted that the resulting product had a physical integrity which resulted in an electrode material which readily flaked-off the screen, making it difficult to cut the screen into a smaller desired size with smooth longitudinal edges. This screen was, therefore, cut to a desired width before the pasty mix was applied thereto.
As will appear, the present invention provides a cadmium electrode which does not require electroplating or charge or discharge operations in its manufacture, and the fabrication thereof utilizes pre-mixed cadmium and cadmium oxide particles held together by a binder applied in a unique way and in a unique sequence in the mixing process, to produce a superior pressed cadmium electrode having the desired proportion of cadmium and cadmium oxide. The binder-held mixture of the active material in the cadmium electrode of the invention has a physical integrity where the particles do not flake-off, and wherein the completed electrode can be cut down to any desired width or length during the mass production thereof, leaving smooth edges along the margins thereof.